Enhanced Photocatalytic and Antimicrobial Performance of Divalent Metal Substituted Nickel Nanostructures for Wastewater Treatment and Biological Applications

The nickel ferrite nanoparticles (NFO) doped with divalent metal ions (Ni_{1 − x}M_xFe₂O₄, x = 0.0, 0.02, 0.09 and M = Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺) were prepared by co-precipitation method and analyzed for their structural, optical, functional group and morphological characterizations. Samples thus prepared were used as a photocatalyst to remove Rhodamine B (RhB) dye from wastewater under sunlight illumination using batch adsorption technique. Doping of NFO led to an increase in dye degradation efficiency. The highest photocatalytic degradation efficiency was obtained for doped NFO NPs (x = 0.02, M = Mn²⁺) nanoparticles (83%) at a pH of 5, 0.030 g of adsorbent dosage in 5 mg/L of dye solution at room temperature. The validity of adsorption data was estimated using nonlinear models of kinetics (1st and 2nd order) as well as isotherm (Langmuir’s model and Freundlich’s model). The nonlinear pseudo 1st order kinetic model (Correlation coefficient, R² = 0.97078) and the Langmuir model (R² = 0.95659) were found to be more suitable than 2nd order (R² = 0.96998) and Freundlich model (R² = 0.91708) for photocatalytic degradation of RhB dye on synthesized samples. The maximum adsorption capacity of RhB dye over synthesized samples is 25.95 mg/g. Sample’s stability after photocatalytic degradation of dye is investigated by FTIR and XRD techniques. The prepared sample’s antibacterial activity was explored for Escherichia coli (max zone of inhibition (ZOI)-15.30 ± 1.00 mm) and Staphylococcus aureus (ZOI-15.50 ± 1.15 mm) using the well diffusion method. Further, the antifungal activity was assessed against soil-borne fungal phytopathogens such as Rosellinia necatrix (max% inhibition-52.75 ± 1.00%) and Fusarium oxysporum (36.55 ± 0.57%). The obtained results revealed that NFO and doped NFO nanoparticles possess excellent photocatalytic, antibacterial and antifungal properties. These nanoparticles could be easily isolated from the water solution as soon as the disinfection activity is completed using an external magnetic field.